CARET is an ongoing double-blind lung cancer chemoprevention trial of the efficacy and safety of the combination of 30 mg beta-carotene and 25,000 IU retinyl palmitate daily in two high-risk populations: (a) male and female current and former smokers recruited primarily from insurance-based sources, and (b) males with extensive occupational asbestos exposure recruited primarily from employment-based sources. We have documented successful recruitment, excellent adherence, and minimal side effects in over 17,600 participants randomized thus far at six study centers. Through March 30, 1994, CARET has randomized 4,060 asbestos-exposed workers, exceeding accrual goals at all five CARET asbestos centers, and 13,560 heavy smokers. Seattle and Portland have exceeded their heavy smoker goals, and Irvine is on track to achieve its goal in August 1994. During the final four-year period, CARET will focus on retention, adherence to protocol, ascertainment of endpoints, monitoring of key design parameters, closeout of the trial, and analysis and publication. Projections indicate that with 14,320 smokers and 4,060 asbestos-exposed participants and 114,750 person-years of follow-up through February 1998, CARET will be capable of detecting a 23% reduction in lung cancer incidence in the two high-risk populations combined, and 27%, 49%, 32%, and 35% reductions in the smokers, female smokers, male smokers, and asbestos-exposed subgroups, respectively. CARET, together with the alpha- tocopherol, beta-carotene study in Finland and the Physicians Health study in the U. S. is a major part of the National Cancer Institute's portfolio of large chemoprevention trials initiated in the 1980's. The Irvine Study Center joined the CARET team in 1991 in order to provide the necessary number (4,300) of current or former smokers to achieve the current smoker accrual goal of 14,320. Using primarily subscriber lists from large-providers (Kaiser, Blue Cross, Health Net), accrual has been achieved in the projected time frame, just 32 months. The Irvine Study Center will continue to emphasize retention and adherence of participants to the CARET protocol; follow-up of participants will be critical to achieving a definitive trial result. Endpoints will increase over the next 4 years, so collecting this information has become a more prominent aspect of the study activities. Our data and processing unit will concentrate on the timely submission and reconciliation of data with the Coordinating Center.